This invention relates to a clutch having a higher holding force and a lower release force through the use of distinct ratios for holding and release force.
Clutches are utilized to selectively transmit or release rotational drive between components in a vehicle driveline. Typically, a clutch is positioned between a vehicle engine and a vehicle transmission. In known clutches, an element is selectively biased against a pressure plate to force the pressure plate to squeeze at least two interleaved disks. One of the disks is connected to rotate with a shaft to be driven and the other disk is fixed to rotate with a clutch cover. The clutch cover is typically connected to the engine to be driven.
In the prior art clutch, a retainer member is connected to move with a release sleeve by a generally conical inner flange on the release sleeve. The retainer rotates with the clutch cover, and thus is able to rotate relative to the sleeve, however, upon axial movement of the sleeve, the retainer typically also moves.
In the prior art clutch a component known as a diaphragm spring forces the retainer in a direction such that it pivots a series of levers to force the pressure plate to squeeze the disks. The diaphragm spring is biased towards a relaxed position, and in trying to move towards its relaxed position its contacts abutment surface on the retainer forcing the retainer to the engaged position at which it causes the levers to hold the pressure plates to squeeze the disks.
When it is desired to release the clutch, the release sleeve is moved to pull the diaphragm spring in a direction allowing the retainer to move away from the engaged position. In the prior art, the point of communication of force from the diaphragm spring holding the retainer in its locked position and point of contact between the retainer and the diaphragm spring are the same.
It would be desirable to have a holding force which is high, and a release force which is low. These two desires have resulted in trade-offs between optimum forces for the two.
In a disclosed embodiment of this invention, the point of contact between the diaphragm spring and the release member is distinct from the point of contact of the diaphragm spring and the retainer biasing the retainer to its holding position. In this way, a large holding force can be created with a much lower release force.
While this application may refer to xe2x80x9cpointxe2x80x9d of contact, of course the contact is actually over a surface area. When the application claims use the terms xe2x80x9cpointxe2x80x9d or xe2x80x9csurfacexe2x80x9d of contact, this should not be read as limiting in any fashion, and would be met by a line contact or a cross-sectional area contact, or other contacts.
In a preferred embodiment the retainer member is connected to be positioned separate from the release sleeve. The release sleeve contacts a radially inner part of the diaphragm spring, and causes the diaphragm spring to be pulled to the release position. When the diaphragm spring is pulled to its release position it also pulls the retainer to the released position. The connection between the diaphragm spring and the release sleeve being at the radially inner end of the diaphragm spring results in a relatively low release force.
However, the connection between the retainer and the diaphragm spring is spaced radially outward from the release point of contact. In this fashion, a multiplier effect from the diaphragm spring force is achieved. The holding force is thus much greater than the release force.
The retainer being separately movable relative to the release sleeve facilitates this benefit.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.